Trayvon's parents, in Washington to attend the National Action Network convention, said they were "confident'' in the criminal justice system and appealed for a peaceful reaction to whatever decision is announced by the Florida special prosecutor. The network, a civil rights group, has been calling for an arrest in the case.

"It's been a nightmare for 44 days,'' said Sybrina Fulton, the slain teenager's mother, referring to the time since her son was killed. "God is holding me up and keeping me. ... I know beyond a shadow of a doubt that justice will be served.''

George Zimmerman:Neighborhood watch captain involved in shooting death of Trayvon Martin

Orlando Sentinel file photo via AP

Benjamin Crump, the family's attorney, said it was "troubling'' for the parents when they heard Zimmerman's lawyers announce this week that they were withdrawing from the case and that they were not certain of Zimmerman's location.

"The killer of Trayvon Martin is unaccounted for,'' Crump said. "His (former) lawyers said he wasn't in the state of Florida. We're very concerned about that.''

Family photo

Trayvon Martin was shot and killed in February.

Rev. Al Sharpton, president and founder of the network, which has been leading a series of protests in wake of Trayvon's death, also called for calm in anticipation of the prosecutor's decision.

"Trayvon Martin's name must not be tarnished,'' Sharpton said. "We denounce anything other than non-violence. We are not in the business of revenge. We are in the business of justice.''

U.S. Attorney General Eric Holder, who also spoke at the convention, pledged that an ongoing federal civil rights inquiry into Trayvon's death would be "a thorough and independent review of the evidence.''

"Although I cannot share where current efforts will lead us from here,'' Holder said, "I can assure you that, in this investigation - and in all cases - we will examine the facts and the law.

"If we find evidence of a potential federal criminal civil rights crime, we will take appropriate action,'' Holder said. "And at every step, the facts and the law will guide us forward.''

In Sanford, the Rev. Harry Rucker, pastor of First Shiloh Baptist Church, said he feared Sanford could erupt in violence if Zimmerman is not charged.

"The system seems to be protecting this individual," said Rucker of Zimmerman. "This whole situation is larger than Trayvon Martin. It's about the ills in our country. It's about hatred and violence. ... There are some real violent activists who want to inflict violence if a warrant isn't issued. They are waiting for an opportunity to get violent."

He said without charges against Zimmmerman, he and others would lose confidence in the criminal justice system.

Rucker said if the right thing is done, Zimmerman will be charged with a crime and a warrant will be issued for his arrest. However, he added that he feared even if charges are filed, locating Zimmerman more than a month after the shooting may prove to be a challenge.

Sentiments ran strong elsewhere in Florida. Charles Favors, past president of the Melbourne-based chapter of the NAACP, said he believes a crime was commited.

"Somebody had to be responsible for that crime," he said. "Whether he's guilty or innocent, the system says you must go to trial. You must have your day in court.